Power transmission device for transmitting thrusting forces

ABSTRACT

A transmission system for transmitting pushing forces along straight and curved paths includes a guide channel (1) and a line of transmission members (10) arranged in the guide channel. The transmission members are acted on by a drive. The transmission members (10) are in contact with each other at end contact faces where the contact faces are formed with mating ring-shaped ridge (11) and a ring-shaped groove, respectively. The ridge (11) and groove (12) are matched to each other such that they are positioned inside each other when the members are arranged coaxially and contacting each other. The cross sections of the ridge (11) and groove (12) are such that ridge and groove are pivotable in relation to each other when engaged. A line of such transmission members arranged in a straight line and pressure loaded forms a buckling-resistant bar which does not exert forces on straight regions (1.2) of an enclosing guide channel (1). In curved guide channel parts (1.1), the transmission members (10) are pivoted in relation to each other, the pivoting movement being a guided one and the pushing force is transmitted through more than a contact point in the pivoted arrangement.

FIELD OF THE INVENTION

This invention is in the field of force transmission devices andconcerns a transmission means for transmitting pushing forces. Theinventive transmission means is designed for pushing operation (i.e.,pressure loadable) and for force transmission along a path which isselectable within broad limits, i.e., straight and also containingfreely selectable curves.

BACKGROUND OF THE INVENTION

According to the state of the art, pressure loadable transmission meansapplicable for curved transmission paths as well as for straighttransmission paths consist, e.g., of a series of transmission membersguided in a suitable guide channel, the members being spherical ordumbbell-shaped. For a line of dumbbell-shaped members to be curveablein all directions, the contact faces of the members are convex as is thecase with spherical members. This means that in both cases thetransmission members are in contact with each other in a very small area(theoretically at one point) whether they are arranged in a straightline or in a curved line. The whole force is transmitted through thiscontact point. Therefore, a line of such transmission members, even astraight line, is very unstable and tends to buckle. Because ofbuckling, the members exert radial forces on the guide means, even on astraight transmission path, resulting in a considerable loss of forcethrough friction and requiring a strong design of the guide means.

In the publication U.S. Pat. No. 3,518,051, a force transmission meansof this general type having spheres as force transmission members isdescribed. Publication U.S. Pat. No. 3,968,861 describes a forcetransmission means of a similar type with dumbbell-shaped transmissionmembers. These members have convex contact faces and, for reducingfriction, comprise rollers rolling on rolling surfaces of the guidemeans.

The publications CH-646762 (or U.S. Pat. No. 4,397,145) and CH-656683describe force transmission means in the form of chains which arepressure or tension loadable and which comprise mutually connectedtransmission members of a substantially spherical form. Such chains alsobuckle easily in straight-line pushed operation and, therefore, must beguided correspondingly.

SUMMARY OF THE INVENTION

An object of the invention is to provide a transmission means fortransmitting pushing forces over freely selectable paths, i.e. curved orstraight paths, which transmission means comprises a line oftransmission members arranged in a guide channel. The inventive forcetransmission means is, compared to known means, able to be operated moreefficiently, i.e. with smaller loss of force. The force transmissionmeans is, all the same, producible in a simple way, even when relativelysmall, and it is driveable with known driving means such as, e.g.,cogwheels, worm gears or hydraulic or pneumatic cylinders.

The inventive force transmission system achieves the above object usingtransmission members which, when arranged in a straight line and pressedagainst each other, form the equivalent of a bar which is considerablymore resistant to buckling than the lines of spheres or ofdumbbell-shaped members with convex contact faces as described above.Due to their resistance to buckling, the members of such a bar causeminimum friction on the guide means as long as they are arranged in astraight line. This not only reduces the necessary operation energy butalso leads to less costly guide channels, having reduced requirement ofloadability and precision, and in which, in specific areas, operation iseven possible without a guide channel.

The inventive force transmission system comprises a line of transmissionmembers and a guide channel in which the members are slidably moved by adrive. The end faces of the members which are in contact with each otherare designed such that the members, in coaxial orientation, form abuckling resistant bar, i.e. the faces are designed such that:

in a straight line of members, two adjacent members contact each otherin a contact area (not in a contact point), wherein the contact area hasno spherical symmetry (no ball and socket joint), extends as far aspossible away from the member axis and is formed such that the resultantof the transmitted force lies on the axis of each member (bucklingresistant bar of members);

a force acting on a straight line of members is advantageouslytransmitted from one member to the neighboring member mainly in radiallyouter regions of the contact area (further stabilization of the bucklingstable bar of elements),

when arranged in contact with each other, the members are centered andkept in a coaxial relationship (promoting prevention of buckling,eccentric force transmission),

when the members are dislocated from a straight line, the members arepivoted relative to each other in a guided manner (maintaining thecentered arrangement); and

advantageously also in a curved line, force is transmitted from onemember to the next one through an area somewhat greater than only atouching point.

Of the two contact faces of two neighboring members facing each other ina line of members of the inventive force transmission means, onecomprises an annular ridge in a radially outer area and the other onehas a corresponding annular groove or at least a half groove. Thereby,the ridge and groove have matched cross sections with a circular arcuateprofile, at least in the region of the top of the ridge and of the baseof the groove (ridge:convex arch; groove:concave arch). This means thatthe ridge lies in the groove when the members are in a coaxialarrangement and there is a contact area between them. It further meansthat when the members pivot out of a coaxial position, this movement isguided due to the fact that the ridge pivots inside the groove.

When the matched ring-shaped grooves and ridges are circular, it ispossible to pivot the transmission members in any desired direction. Insuch a case, the contact area between two members is constituted by atleast part of the groove or ridge surface in a coaxial arrangement, andis reduced to a contact line running perpendicular to the groove andridge when the members are pivoted.

When the ring-shaped grooves and ridges have the form of polygons, thepossible pivoting directions are restricted to directions perpendicularto the polygon sides, wherein in the pivoted position a contact surfacebetween ridge and groove is maintained along one polygon side.

The grooves and corresponding ridges and/or the centers of the faces areadvantageously shaped such that the centers of the faces of twocoaxially arranged members are not in contact with each other, i.e. sothat no force is transmitted through the center.

The groove-and-ridge form of the contact faces acts in a centeringmanner. The transmission members of the inventive transmission means arepivotable in relation to each other in any direction (circular grooveand ridge) or in a plurality of predetermined directions (polygon-shapedgroove and ridge) and still, when in a straight line, the memberstransmit force like a bar, i.e. the line of members shows considerableresistance to buckling. Due to shifting the load to radially outerregions of the faces, the resistance to buckling is additionallyincreased. Due to the circular arcuate profile of the ridge top and thegroove base, a guided pivoting movement of two neighboring members ismade possible, in which movement the members are maintained centered.Two pivoted members are in contact along at least a contact line asopposed to a contact point between two spheres or two spherical faces.

The guide channel of the inventive force transmission means takes up theforce in curved regions. In straight regions, however, it merely servesas a trap for the transmission members and possibly for taking upexternal radial forces acting on the transmission members. Because astraight line of members of the inventive force transmission means actslike a pressure-loaded bar, the guiding function of the guide channelbecomes virtually unnecessary in such areas and the channel can bedesigned correspondingly.

The transmission members of the inventive force transmission means can,depending on the application, be totally independent of each other orthey can be mutually connected. Suitable connection means are designedto be flexible in a way that permits pivoting of the members in relationto each other. The connection means can at the same time have anadditional, centering function and/or a position restoring function,i.e. be designed such that they force the members back into a coaxialorientation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the inventive force transmission means are described inmore detail with reference to the following drawings wherein:

FIG. 1 is a partial sectional view of an embodiment of the inventiveforce transmission means, partly sectioned parallel to the axis of theguide channel;

FIG. 2 is an enlarged longitudinal sectional view through the contactarea between two neighboring transmission members of an inventive forcetransmission means which are shown coaxially (in unbroken lines) andpivoted in relation to each other (in broken lines);

FIGS. 3 and 4 are schematic views of two applications of the inventiveforce transmission means;

FIG. 5 is a transverse sectional view of an inventive force transmissionmeans in the region of a drive;

FIG. 6 is a perspective view of transmission members of an inventiveforce transmission means with polygon-shaped faces;

FIGS. 7 and 8 are schematic transverse sectional views of inventiveforce transmission means with members substantially according to FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a part of an embodiment of a force transmission means inaccordance with the invention. A guide channel 1 has curved and straightregions 1.1 and 1.2, respectively. The guide channel is sectioned alongits axis. In guide channel 1 is a line of transmission members 10, shownpartly in section along their axes.

Transmission members 10 comprise, as described above, two contact faceseach, one end being formed with an annular circular ridge 11 and theother end being formed with a corresponding annular circular groove 12.In order to allow mutual pivoting of the members around an axisperpendicular to the axis of the members, the outer wall of the grooveis reduced. Of course, it is possible also to form a line of alternatingmembers of two types, one type being formed with grooves on both contactfaces and the other type being formed with ridges on both contact faces.

The shapes of transmission members 10 between the end faces is notrelevant to the invention. If, e.g., the members are to be driven with acog-wheel or a similar driving means, they must have a form which can begripped by the driving means, e.g., comprising one or two locations(indicated generally at 13) having a reduced cross section. If themembers are to be movable around curves which are relatively tightrelative to the member length, the members are advantageously shapedlike dumbbells with substantially spherical ends.

The transmission members may comprise an axial bore 14. This displacesforce transmission to the radially outer region of the groove and ridgeand, in addition, may receive a cable for transmission of electric poweror electric signals to a predetermined location on the line of members,the cable being loosely laid through the line of members. Such a cablecan additionally take over the function of a loose connection of thetransmission members (see also FIG. 6).

As an example for an application, a gripper 20 is shown arranged on oneof the transmission members, which gripper protrudes through aslot-shaped opening 21 in guide channel 1 to the outside and with whichgripper, e.g., objects are movable along the path of guide channel 1.

FIG. 1 shows clearly how the transmission members form a stable bar whenthey are arranged in a straight line as seen in the left-hand part ofthe figure. This is due to the fact that, at least in the region ofgroove and ridge positioned inside each other, the members are incontact with each other and they are held in a stable, centeredposition. It can also be seen from FIG. 1 that the members are displacedtoward the radially outside portion of the channel in its curved region,which region of the channel must be able to take up the resultingforces. In opposition to this, the guide channel does not perform aguiding function in straight region 1.2 (the members do not touch theguide channel in this region, as shown). The guide channel is to fulfillstability requirements on the outsides of curves only and there arehardly any requirements concerning precision of the inner channel cavityin relation to the radial extension of the transmission members.

FIG. 2 shows, on a larger scale, the contact region between twoneighboring, abutting transmission members 10.1 and 10.2, again in asection along their axis A, the transmission members being substantiallysimilar to those in FIG. 1. Of member 10.1, the face with groove 12 isshown, and of member 10.2 is shown the face with ridge 11. Member 10.1is shown in unbroken lines in a coaxial position in relation to member10.2 and in broken lines, in a position pivoted in relation to member10.1. The pivoting symbolized by the arrow S is guided by the at leastpartly circular arcuate profile of the cross sections of groove andridge. A defined pivoting axis M extends through the center of thiscircle. During pivoting, groove and ridge remain engaged. For circulargroove and ridge, their contact during pivoting is theoreticallyrestricted to a radial line perpendicular to the pivoting axis and liesin the section plane of FIG. 2.

Transmission members 10.1 and 10.2 according to FIG. 2 differ from thetransmission members according to FIG. 1 in that they do not comprise anaxial bore (14). For still displacing force transmission to the radiallyouter regions of the contact faces, ridge 11 is advantageously higherthan the depth of groove 12. Thus, contact in central region 15 of thefaces and force transmission in this central region is prevented.

FIG. 3 shows an application of the inventive force transmission means.It is an endless loop of a guide channel 1 closed on itself in whichloop the transmission members 10 are arranged in such a number that theytouch each other. Members 10 are moved pushing each other in one or theother direction in guide channel 1 by means of a chain wheel 30 the cogsof which reach into a suitable opening in guide channel 1 to interactwith the transmission members. Guide channel 1 can, e.g., comprise aslot-shaped opening (21, FIG. 1) extending over its whole length throughwhich opening grippers arranged on the members protrude outwardly (20,FIG. 1) for moving objects around the whole loop, 30 through part of theloop or to and fro over part of the loop.

The channel loop of FIG. 3 consists of two straight parts connected bytwo curved parts, all parts being arranged in a plane. obviously, theloop can have any form, i.e., it is not a condition for it to bearranged in a plane.

FIG. 4 shows a further application of the inventive force transmissionmeans. The guide channel is not closed on itself and comprises betweentwo curved regions 1.1, a straight region 1.2. At the two ends of thestraight part, two mutually coupled drive wheels 30.1 and 30.2 areprovided for acting on the line of transmission members arranged in thechannel.

The force transmission means according to FIG. 4, e.g., serves fordisplacing a part 31 of the device (shown very 10 schematically) orseveral such parts to and fro. The total length of guide channel 1 andthe cumulative length of the line of transmission members arranged inthe channel is selected such that the line reaches at least from onedrive wheel to the other one (30.1 or 30.2, respectively) when the partof the device is in one of the predetermined extreme positions. Thecurved parts 1.1 of the guide channel are orientated such thattransmission members 10 located therein are driven by gravity towardstraight part 1.2. Thereby, the members are not exposed to anytransmission force, i.e., there are virtually no friction and wearingforces either on the curved channel parts nor on the straight channelpart.

For the application shown in FIG. 4, a correspondingly driven bar couldbe used instead of the line of transmission members. Function andoperation characteristics of the bar between the two driving wheels 30.1and 30.2 would be exactly the same as the function of the bar formed bythe transmission members. The advantage of the inventive forcetransmission means compared to the bar is the curved channel ends 1.1,which constitute, especially in the case of a long straight part, aconsiderable amount of space saved.

FIG. 5 shows a cross section through a driving wheel 30 gripping intothe guide channel and cooperating with a transmission member 10. Agripper 20 is arranged on transmission member 10, which gripperprotrudes out of the guide channel through a slot-shaped opening 21.

FIG. 6 shows two transmission members 10.3 pivoted in relation to eachother. Contrary to the transmission members of FIGS. 1 and 2, thecontact faces of the members are square and comprise a groove 12 or aridge 11 respectively having the form of a quadrangular ring, althoughgroove and ridge have, e.g., the same cross section as the ones shown inFIG. 2.

Compared to transmission members with circular grooves or ridgesrespectively, these members 10.3 can only be pivoted in a controlledmanner in four directions at right angles to each other. For morepivoting directions, hexagonal, octagonal or generally polygon-shapedrings of ridge and groove are possible.

In FIG. 6, a cable 16 laid through the axial bores of the members isalso shown as an example of a loose connection means for looselyconnecting the transmission members.

Grooves and ridges on contact faces of transmission means designed to bepolygon-shaped need not form a continuous ring. They can, e.g., beinterrupted at the edges of the polygon.

FIGS. 7 and 8 show in cross section, transmission members 10.3substantially according to FIG. 6 positioned in a guide channel 1.3 or1.4, respectively. These figures show that the transmission members 10.3having a square face are applicable in square guide channels (1.3) aswell as in circular ones (1.4). In a guide channel with a round crosssection it is advantageous to provide means for maintaining therotational alignment of the transmission members.

We claim:
 1. A transmission system for transmitting pushing forces alongstraight and curved paths comprisinga guide channel; a plurality oftransmission members movable in said guide channel; a drive coupled tosaid transmission members for moving said transmission members in atleast one direction in said guide channel; each of said transmissionmembers comprising contact faces for contacting adjacent transmissionmembers and transmitting forces from said drive, each said contact facehaving a center and including at least one of a generally annular ridgeand a generally annular groove, said ridges and grooves being spacedradially outwardly from said center on each contact face; saidtransmission members being positioned so that a ridge on a contact facematingly engages with a groove on an abutting contact face and so thatforce is transmitted through said ridges and grooves from said drivethrough said transmission members; and said mating ridges and groovesbeing shaped so that a transmission member is pivotable relative to anabutting transmission member with said ridge and groove engaged.
 2. Atransmission system according to claim 1 wherein each said ridgecomprises an arcuate cross-section and each said groove has an arcuatecross-section of substantially the same radius as said ridge.
 3. Atransmission system according to claim 1 wherein each said ridge andgroove is generally circular.
 4. A transmission system according toclaim 1 wherein each said ridge and groove is polygonal.
 5. Atransmission system according to claim 1 wherein, when adjacent ones ofsaid contact faces are abutting, said centers of said contact faces arespaced apart.
 6. A transmission system according to claim 1 includingconnection means for loosely interconnecting said transmission memberswith each other.
 7. A transmission system according to claim 6 whereinsaid transmission members comprise an axial bore.
 8. A transmissionsystem according to claim 7 wherein said connection means comprises acable through said axial bores of said transmission members.
 9. Atransmission system according to claim 1 wherein said drive comprises achain wheel having cogs engaging reduced cross-section portions of saidtransmission members, said guide channel having an opening for saidchain wheel.
 10. A transmission system according to claim 1 wherein saidguide channel is mounted so that said transmission members are driventoward said drive by gravity.
 11. A transmission system according toclaim 1 wherein said guide channel comprises an endless loop and saidtransmission members have a cumulative length substantially equal to thelength of said guide channel.
 12. A transmission system according toclaim 1 wherein said guide channel has two ends, said system comprisingtwo drives spaced a distance apart, and wherein the cumulative length ofsaid transmission members is less than the length of said guide channel.